In the most extreme cases: killing works too. Bin Laden / Anwar Al-Awlaki. Both were more "inspirational" figures than actual day-to-day management, but their ability to spread and inspire others was still better than the typical ISIS / Al Qaeda member.
Destroying the mouthpiece works. Full on killing / murder is only condoned in war-like situations, but there are "softer powers" like knocking websites offline. Sure, they are tenacious and spring up again (and will continue to do so unless we actually kill them), but every hour those websites are down is another hour where they fail to recruit members into their philosophy.
Considering that we refuse to utilize the ultimate solution (assassination / killing) vs these people, the best we can hope for is to just inconvenience them over-and-over again. Its just like banning troll accounts at a highly-moderated forum. The trolls inevitably pickup a new VPN and get to post again for a few hours. The idea isn't to stop the troll from talking, its to hamper the troll from talking.
> They'll still be talking to others, you fundamentally cannot stop that. The only difference is that we are depriving ourselves of the chance to challenge them on their bigoted and hateful beliefs.
Nah, we can totally do that. You and I can talk about white-nationalism right now. Do you believe that white people are "being replaced" by immigrants? And if so, do you think its a long-term negative for this country?
Bam. Now we can talk about the subject. And I trust you (and most random strangers) to have decent opinions on the subject. The issue is that a large group of white-nationalists are working to recruit young people into their hateful philosophy, and to grow their base. And this growth includes violent action (with them cheering the actions of El Paso shooter + New Zealand's shooter).
I'm not against intelligent discussion of these subjects. I'm against the recruitment and growth of power of hate-groups.